1. Field of the Invention
The present invention generally relates to an apparatus for kneading material of cosmetics such as lipstick, food such as chocolate, material of resin product, soap and the like and/or pulverizing fine particles contained in the material, and a method for manufacturing soap using the pulverizing/kneading apparatus.
2. Description of the Related Art
According to a known method for manufacturing solid soap, for an example, after neat soap is dried, extruded in pellet configuration by a plodder then, pigment and perfume are mixed with the dried ground of the extruded pellet soap, the mixture is kneaded, and an extrusion molding is then carried out. But hard and fine particles existing on the surface of the soap molded according to this method are rough to the touch. This is because fine particles contained in the soap compound have not been pulverized sufficiently.
Conventionally, there have been provided some pulverizing/kneading apparatuses for solving this problem. One of the known apparatuses for kneading the material, such as dried neat soap, to make a uniform mixture is of a roll mill type in which rollers are mounted on several shafts parallel with each other so that the rollers are in contact with each other. Another known apparatus is of a paddle type in which paddles of a convex lens configuration in section are mounted on two shafts in a barrel parallel with each other so that the axes of the paddles form a phase of 90.degree. with each other, as disclosed in Japanese Patent Laid-Open Publication No. 1-190800. In the kneading apparatuses of the above-described type, the amount of fine particles contained in the material which are pulverized in the space between rollers or between paddles is small because the contact area between the rollers or between the paddles is small, and many fine particles remain contained in the material discharged from the apparatus because many fine particles pass without being pulverized between the rollers or the paddles or between the paddles and a barrel which accommodates the paddles. Therefore, after the material is molded, small hard particles existing on the surface of a molded product of the material are rough to the touch. Thus, these apparatuses are incapable of sufficiently solving the problem.
As a kneading apparatus to solve the problem that the surface of the product is rough because fine particles are in the material, a gear compounder is known, for example in a Japanese Publication "KNEADING APPARATUS" (page 194) published on Sep. 20, 1986 in Japan. The gear compounder comprises several pairs of shafts in parallel. The two shafts of each pair are parallel with each other in a horizontal plane. The pairs are arranged vertically. In each pair, the shafts have kneading double helical gears engaging with each other. In the gear compounder, fine particles contained in the material are pulverized between teeth in mesh and the material are kneaded by the rotation of each gear by moving the material downward from above so that it passes between each pair of gears.
If the viscosity of the material is low, the gear compounder is capable of sufficiently kneading the material and pulverizing particles contained therein. However, if the material is solid or the viscosity thereof is very high, the material sticks to the tooth surface and hardly flows downward under the gears. Thus, the amount of the material which can be kneaded per unit time is very small, and the apparatus requires enlargement to increase the amount which can be kneaded.